I was running the whole ant-clean-test in a loop last night for LUCENE-2122 and had this error in IndexWriter occur once in 30+ runs. I now there has been some work on spurious failures here lately and thought I'd add this on the chance it'd help anyone tracking this issue. Didn't see a JIRA...
I updated the trunk yesterday (12-Dec) afternoon sometime.... [junit] Testcase: testMaxBufferedDocsChange(org.apache.lucene.index.TestIndexWriterMergePolicy): FAILED [junit] maxMergeDocs=2147483647; numSegments=11; upperBound=10; mergeFactor=10 [junit] junit.framework.AssertionFailedError: maxMergeDocs=2147483647; numSegments=11; upperBound=10; mergeFactor=10 [junit] at org.apache.lucene.index.TestIndexWriterMergePolicy.checkInvariants(TestIndexWriterMergePolicy.java:234) [junit] at org.apache.lucene.index.TestIndexWriterMergePolicy.testMaxBufferedDocsChange(TestIndexWriterMergePolicy.java:164) [junit] at org.apache.lucene.util.LuceneTestCase.runBare(LuceneTestCase.java:212) [junit] FWIW Erick